Truck conveyors for conveying long articles have heretofore been known, such as those described in Japanese Patent Publications Nos. 38391/72, 15272/78 and 15273/78.
In the truck conveyor disclosed in the Japanese Patent Publication No. 38391/72, a plurality of trolleys (four trolleys in the embodiment shown therein) are connected to one another through a traction bar (40) to constitute a traction trolley unit. The overall length of this traction trolley unit is made a little longer than the length of an elongated article carried on a truck (10) by either increasing the number of trolleys or selecting a suitable length of a traction bar according to the length of the elongated article. It is thereby possible to stop and store the truck even on a curved conveyance path without a succeeding truck colliding with the rear end of the stopped preceding truck. It is also possible to separate only the traction unit from the truck and lead it to a traction trolley unit storage path.
However, the overall length of the traction trolley unit, consisting of plural trolleys connected together through a traction bar, must be adjusted by either increasing the number of trolleys or selecting a suitable traction bar from among traction bars of various lengths according to the length of the elongated article to be conveyed. Additionally, for storing the traction trolley unit having a length greater than the elongated article to be conveyed, an increase in the length of the storage path is unavoidable. Moreover, as a spacer bar is provided between a trolley rail and a chain carrier rail of the trolleys, the distance between the two rails must be large.
In the truck conveyors disclosed in Japanese Patent Publications Nos. 15272/78 and 15273/78, a leading trolley (14) positioned in front of a truck and a rearmost trolley (15) positioned behind the truck are each connected directly to the truck (7) through universal joints and a spacer bar (12). Only the leading trolley (14) and the rearmost trolley (15) are guided within a rail (3), and therefore the direction of the truck cannot be controlled unless there is a rail (4) for guiding the running direction of the truck. Particularly on a curved path, it is possible that the centrifugal force acting on the truck will cause the truck to go off a predetermined running path, thus resulting in the spacing between the leading trolley (14) and the rearmost trolley (15) being shortened and the function of preventing a rear-end collision being no longer attainable. Moreover, whenever a flange is provided on a wheel, or the rail includes a channel for guiding the truck, the guide portion for the flange or the channel becomes an obstacle at the switch rail portion provided in the truck path switching position. Furthermore, by disconnecting the truck from the trolleys and removing it from its running path, it is necessary to remove the spacer bar (12) by removing connection pins. In addition, since the spacer bar protrudes upwardly from the floor on which the trucks move during the traction operation, personnel are liable to trip over it or articles conveyed on the floor are liable to collide with it rendering the trucks inoperative.